1. Field of the Invention
The present invention relates to coaxial cable unit, test apparatus and CPU system. More particularly, the present invention relates to a coaxial cable unit, a testing apparatus and a CPU system including the coaxial cable unit for supplying a device with an electric current generated by a power source.
2. Description of the Related Art
FIG. 1 is a block diagram showing the configuration of a testing apparatus 100 according to the conventional art relating to the present invention.
The testing apparatus 100 supplies a DUT (Device Under Test) 110 with a predetermined electric current and performs a current application voltage test to measure the voltage applied to the DUT 110. The testing apparatus 100 includes a power source 120, a coaxial cable unit 130, a detecting unit 160 and a judging unit 170.
The power source 120 generates an electric current and sends it to the coaxial cable unit 130. The coaxial cable unit 130 includes a first coaxial cable 140 and a second coaxial cable 150 and supplies the current generated by the power source 120 to the DUT 110.
The first coaxial cable 140 includes a first internal conductor 142 and a first external conductor 144 provided around the first internal conductor 142 via an insulator. The first internal and external conductors 142 and 144 conduct the current from the power source 120 towards the DUT 110. The second coaxial cable 150 includes a second internal conductor 152 and a second external conductor 154 provided around the second internal conductor 152 via an insulator. The second internal and external conductors 152 and 154 conduct the current from the DUT 110 towards the power source 120.
The detecting unit 160 detects the voltage applied to the DUT 110 when the current generated by the power source 120 is supplied to the DUT 110, and sends the detected voltage to the judging unit 170. The judging unit 170 judges the quality of the DUT 110 based on the voltage detected by the detecting unit 160.
According to the testing apparatus 100 in the conventional art relating to the present invention, through the coaxial cable unit 130, the current application voltage test can be performed with a large current supplied to the DUT 110.
FIG. 2 shows an equivalent circuit of the coaxial cable unit 130 according to the art relating to the present invention.
The first coaxial cable 140 conducts the current from S1 to S2. The equivalent circuit of the first internal conductor 142 includes a plurality of coils 146, each of which has self-inductance L1 and is coupled in series with one another. The equivalent circuit of the first external conductor 144 includes a plurality of coils 148, each of which has self-inductance L2 and is coupled in series with one another.
The second coaxial cable 150 conducts the current from G2 to G1. The equivalent circuit of the second internal conductor 152 includes a plurality of coils 156, each of which has self-inductance L1 and is coupled in series with one another. The equivalent circuit of the second external conductor 154 includes a plurality of coils 158, each of which has self-inductance L2 and is coupled in series with one another.
If the current generated by the power source 120 is changed, the current flowing through the first internal conductor 142 is changed, so the magnetic flux generated by the coils 146 is changed. Accordingly, a self-induction electromotive force is generated in the first internal conductor 142. The generated self-induction electromotive force acts to impede the flow of the current in the first internal conductor 142. In addition, if the current generated by the power source 120 is changed, the current flowing through the first external conductor 144 is changed, so the magnetic flux generated by the coils 148 is changed. Accordingly, the magnetic flux crossing the coils 146 is changed, and then a mutual induction electromotive force is generated in the first internal conductor 142. The generated mutual induction electromotive force acts to impede the flow of the current in the first internal conductor 142.
In this way, for each of the first external conductor 144, the second internal conductor 152 and the second external conductor 154, the generated self-induction and mutual induction electromotive forces act to impede the flow of the currents in the respective conductors.
Due to the induced electromotive forces acting in the testing apparatus 100 in the art relating to the present invention, the responsiveness of output current to the change in input current is decreased with regard to the coaxial cable unit 130. Particularly, by these induced electromotive forces, the testing apparatus 100 needs more time from when the current generated by the power source 120 is changed to when the current supplied to the DUT 110 is changed. Therefore, in case a sudden change in current is needed, it is difficult to perform the test highly accurately.